The present invention relates to a method and apparatus for producing a substrate whose surface includes a metallic wire, by polishing the substrate surface.
JP-A-2-278822 discloses a polishing method using a polishing liquid including an etching liquid and abrasive power to polish a substrate chemically and mechanically. JP-A-8-83780 discloses a polishing method using a polishing liquid including an etching liquid to polish a substrate chemically and mechanically. JP-A-9-306881 discloses a polishing method using a polishing liquid including an etching liquid without abrasive powder to polish a substrate chemically and mechanically. JP-A-10-125880 discloses a polishing method using a polishing liquid including an alkaline etching liquid without abrasive powder to polish a substrate chemically and mechanically. JP-A-8-64562 and A new Slurry-free CMP Technique for Cu Interconnects published on Semi-Technology Symposium 1998 disclose a polishing method using a polishing pad including abrasive powder and a polishing liquid without abrasive powder to polish a substrate. The publication of U.S. Pat No. 5,597,341 discloses a structure for detecting a frictional force between a polishing pad and a substrate during polishing by measuring a polishing pad rotational driving force and a substrate rotational driving force.
An object of the present invention is to provide a method and apparatus for producing a substrate whose surface includes a metallic wire by polishing the substrate surface, in which method and apparatus a decrease of a frictional coefficient between a substrate surface and a polishing pad surface or a polishing depth increasing velocity in accordance with an increase of a relative movement velocity between the polishing pad surface and the substrate surface to be polished by the polishing pad surface is restrained. The frictional coefficient between the substrate surface and the polishing pad surface is determined in the present invention as (a measured frictional force therebetween/a pressing force applied therebetween).
In the present invention for producing a substrate whose surface includes a metallic wire by polishing the substrate surface,
a polishing liquid is supplied into a clearance between the substrate surface and a polishing pad surface of a polishing pad, which polishing liquid includes an acid for dissolving an oxidized part of the substrate surface and is prevented substantially from including solid abrasive powder, and
a relative movement is generated between the substrate surface and the polishing pad surface while pressing the substrate surface against the polishing pad surface with the polishing liquid between the substrate surface and the polishing pad surface so that the dissolved oxidized part of the substrate surface is removed from the substrate.
Since the polishing liquid which, includes the acid for dissolving the oxidized part of the substrate surface and is prevented substantially from including solid abrasive powder is used to polish the substrate surface, a viscosity of the polishing liquid is kept small while preventing an increase in number of defects on the substrate surface by the abrasive powder so that the decrease of the frictional coefficient between the substrate surface and the polishing pad surface or a polishing depth increasing velocity in accordance with an increase of a relative movement velocity between a polishing pad surface and the substrate surface to be polished by the polishing pad surface is restrained. The polishing liquid may further include an oxidizing agent (including, for example, hydrogen peroxide, phosphoric acid, nitric acid, or the like) for oxidizing a part of the substrate surface so that the part of the substrate surface becomes brittle, a protective film forming agent (including, for example, benzotriazole (BTA), a derivative of benzotriazole or the like) for forming a protective film on the substrate surface so that an oxidizing proceeding on a bottom part of a substrate surface micro-shape of roughness by the oxidizing agent is restrained, and a surfactant for chemical stability of the polishing liquid. A main component of the polishing pad is, for example, foamed polyurethane polymer, foamed fluoro-carbon polymer or the like.
If the oxidized part of the substrate surface is dissolved in the polishing liquid, and the polishing liquid in which a concentration of the dissolved oxidized part of the substrate surface is smaller than a concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface so that a concentration of the dissolved oxidized part of the substrate surface in the polishing liquid to be supplied to the clearance between the substrate surface and the polishing pad surface is decreased, a dissolution, diffusion or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated so that a decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity is restrained although a floating force between the substrate surface and the polishing pad surface increases in accordance with the increase of relative movement velocity between the polishing pad surface and the substrate surface.
If the relative movement between the substrate surface and the polishing pad surface is being generated when the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface, both of the supply of the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface into the polishing liquid on the polishing pad surface and the removal of the oxidized part of the substrate surface from the substrate surface and/or polishing pad surface are simultaneously performed with the relative movement so that the dissolution, diffusion or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated to restrain the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity.
If the substrate surface is prevented from contacting the polishing pad surface when the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface, the concentration of the dissolved oxidized part of the substrate surface is effectively decrease over a large area of the polishing pad surface without being obstructed by the substrate surface.
It is effective for decreasing the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface that the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is prevented substantially from including the dissolved oxidized part of the substrate surface.
If the polishing liquid is stirred in a direction perpendicular to a direction of the relative movement so that the concentration of dissolved oxidized part of the substrate surface in the polishing liquid is made uniform in the direction perpendicular to the direction of the relative movement, the removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is uniformly performed in the direction perpendicular to the direction of the relative movement so that the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity is restrained. When the polishing pad rotates on a rotational axis, and a stirring member slides radially inward on the polishing pad surface, a discharge of the polishing liquid from the polishing pad surface by a centrifugal force is restrained. When the polishing pad rotates on the rotational axis, and the stirring member slides radially outward on the polishing pad surface, a discharge of the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is large from the polishing pad surface is accelerated. The polishing liquid may be stirred while the substrate surface contacts the polishing pad surface to polish the substrate surface or while the substrate surface is prevented from contacting the polishing pad surface.
If the polishing liquid whose acidity is larger than an acidity of the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface so that the acidity of the polishing liquid to be supplied to the clearance between the substrate surface and the polishing pad surface is increased, the dissolution, diffusion or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated so that the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity is restrained although the floating force between the substrate surface and the polishing pad surface increases in accordance with the increase of relative movement velocity between the polishing pad surface and the substrate surface.
As shown in FIG. 4b, during the polishing with the polishing liquid including the acid for dissolving the oxidized part of the substrate surface, the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity is small at a relatively low velocity of the relative movement although the polishing is continued for a relatively long time, on the other hand, the frictional Coefficient between the polishing pad surface and the substrate surface or the polishing depth increasing velocity decreases abruptly at a relatively high velocity of the relative movement when the polishing has been continued for the relatively long time (for example, 1-5 minutes). As shown in FIG. 4a showing a relationship between the velocity of the relative movement and the frictional force between polishing pad surface and the substrate surface measured when the polishing has been continued for the relatively long time (for example, 1-5 minutes), the frictional coefficient between the polishing pad surface and the substrate surface or the polishing depth increasing velocity is large at the relatively low velocity of the relative movement lower than a critical relative movement velocity range, the frictional coefficient between the polishing pad surface and the substrate surface or the polishing depth increasing velocity is low at the relatively high velocity of the relative movement higher than the critical relative movement velocity range, and a change between the frictional force or polishing depth increasing velocity at the relatively low velocity and the frictional force or polishing depth increasing velocity at the relatively high velocity is critical. In the present invention, by at least one of supplying additionally the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface into the polishing liquid on the polishing pad surface so that the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid to be supplied to the clearance between the substrate surface and the polishing pad surface is decreased, supplying additionally the polishing liquid whose acidity is larger,than the acidity of the polishing liquid on the polishing pad surface into the polishing liquid on the polishing pad surface so that the acidity of the polishing liquid to be supplied to the clearance between the substrate surface and the polishing pad surface is increased, and supplying additionally a surfactant into the polishing liquid on the polishing pad surface so that the volume of the surfactant on the polishing pad surface is increased, the dissolution, diffusion or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated so that the frictional force or polishing depth increasing velocity is prevented from changing abruptly and critically at the critical relative movement velocity range.
If the relative movement between the substrate surface and the polishing pad surface is being generated when the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface, both of the supply of the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface into the polishing liquid on the polishing pad surface and the removal of the oxidized part of the substrate surface from the substrate surface and/or polishing pad surface are simultaneously performed with the relative movement so that the dissolution, diffusion or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated to restrain the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity.
If the substrate surface is prevented from contacting the polishing pad surface when the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface is added and supplied into the polishing liquid on the polishing pad surface, the acidity in the polishing liquid is effectively increased over the large area of the polishing pad surface without being obstructed by the substrate surface.
It is preferable that the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface is prevented substantially from including the dissolved oxidized part of the substrate surface. If the polishing liquid is stirred in a direction perpendicular to a direction of the relative movement so that the acidity of the polishing liquid is made uniform in the direction perpendicular to the direction of the relative movement, the removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate is uniformly performed in the direction perpendicular to the direction of the relative movement so that the decrease of frictional coefficient between the polishing pad surface and the substrate surface or of polishing depth increasing velocity is restrained.
A stirring member may grind the polishing pad surface when the stirring member slides on the polishing pad surface to stir the polishing liquid. The stirring member maybe prevented substantially from grinding the polishing pad surface when the stirring member slides on the polishing pad surface to stir the polishing liquid.
If the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is supplied into the clearance between the substrate surface and the polishing pad surface after being stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface, the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is small and constant is supplied into the clearance between the substrate surface and the polishing pad surface. If the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is smaller than the concentration of the dissolved oxidized part of the substrate surface in the polishing liquid on the polishing pad surface is supplied into the clearance between the substrate surface and the polishing pad surface before being stirred by the stirring member and subsequently is stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface after passing through the clearance between the substrate surface and the polishing pad surface, the polishing liquid in which the concentration of the dissolved oxidized part of the substrate surface is small is effectively supplied into the clearance between the substrate surface and the polishing pad surface.
If the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface is supplied into the clearance between the substrate surface and the polishing pad surface after being stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface, the polishing liquid whose acidity is large and constant therein is supplied into the clearance between the substrate surface and the polishing pad surface. If the polishing liquid whose acidity is larger than the acidity of the polishing liquid on the polishing pad surface is supplied into the clearance between the substrate surface and the polishing pad surface before being stirred by the stirring member and subsequently is stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface after passing through the clearance between the substrate surface and the polishing pad surface, the polishing liquid whose acidity is large is effectively supplied into the clearance between the substrate surface and the polishing pad surface.
It is preferable for finely finishing a roughness of the substrate surface that, during the relative movement, a pressing force between the polishing pad surface and the substrate surface is limited to such a degree that the polishing pad surface is prevented from removing from the substrate the oxidized part of solid state which is undissolved by the acid and the oxidized part is dissolved by the acid in the polishing liquid on the polishing pad surface after being removed from the substrate so that the oxidized part of the substrate surface is prevented from being included by the polishing liquid on the polishing pad surface in a solid state. The degree of the pressing force between the polishing pad surface and the substrate surface for preventing the polishing pad surface from removing from the substrate the oxidized part of solid state which is undissolved by the acid is determined experimentally and/or experientially.
If a frictional force between the substrate surface and the polishing pad surface is measured to detect a decrease of the frictional force (for example, decrease from a desired frictional force by 10%) and the pressing force of the substrate surface against the polishing pad surface and/or a pressing force of the stirring member or a dressing member for cutting the polishing pad surface to roughen the polishing pad surface against the polishing pad surface is increased in response to the detected decrease of the frictional force so that the decrease of the frictional force is restrained, the decrease of polishing depth increasing velocity is restrained. If the velocity of the relative movement between the substrate surface and the polishing pad surface is decreased in response to the detected decrease of the frictional force so that the decrease of the frictional force is restrained, the decrease of polishing depth increasing velocity is restrained. The oxidized part of the substrate surface includes an oxidized metallic component. The polishing liquid may include the abrasive powder of not more than 0.5 weight percent, preferably not more than 0.1 weight percent.
If a surfactant (sulfonate type or polyacrylate type, for example, poly-ammonium-acrylate, poly-ammonium-methacrylate, benzene-ammonium-sulfonate, benzene-potassium-sulfonate or the like) is added and supplied into the polishing liquid on the polishing pad surface so that a volume of the surfactant on the polishing pad surface is increased and bubbles of the polishing liquid are generated or the generation of the bubbles of the polishing liquid is accelerated on the polishing pad surface, the dissolution or removal of the oxidized part of the substrate surface from the polishing pad surface and/or the substrate and/or the diffusion of the dissolved oxidized part of the substrate surface in the polishing liquid is accelerated lso that the frictional force or polishing depth increasing velocity is prevented from changing abruptly and critically at the critical relative movement velocity range. If the relative movement between the substrate surface and the polishing pad surface is being generated when the surfactant is added and supplied into the polishing liquid on the polishing:pad surface, the removal of the dissolved oxidized part of the substrate surface from the polishing pad surface and/or the substrate is accelerated by the surfactant. If the substrate surface is prevented from contacting the polishing pad surface when the surfactant is added and supplied into the polishing liquid on the polishing pad surface, the diffusion of the dissolved oxidized part of the substrate surface in the polishing liquid is accelerated on most of the polishing pad surface. If the surfactant is supplied into the clearance between the substrate surface and the polishing pad surface after being stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface, the polishing liquid in which the surfactant is uniformly distributed is supplied into the clearance between the substrate surface and the polishing pad surface so that the oxidized part of the substrate surface is removed uniformly between the substrate surface and the polishing pad surface. If the surfactant is supplied into the clearance between the substrate surface and the polishing pad surface before being stirred by the stirring member and subsequently is stirred by the stirring member to be mixed with the polishing liquid on the polishing pad surface after passing through the clearance between the substrate surface and the polishing pad surface, the removal of the dissolved oxidized part of the substrate surface from the substrate surface and/or the polishing pad surface is surface is accelerated.
If a frictional force between the stirring member or the dressing member and the polishing pad surface is measured to detect a decrease of the frictional force (for example, decrease from a desired frictional force by 20%) and the pressing force of the stirring member or dressing member against the polishing pad surface and/or the pressing force of the substrate surface against the polishing pad surface is increased in response to the detected decrease of the frictional force so that the decrease of the frictional force is restrained, the decrease of polishing depth increasing velocity is restrained. If the velocity of the relative movement between the substrate surface and the polishing pad surface is decreased in response to the detected decrease of the frictional force so that the decrease of the frictional force is restrained, the decrease of polishing depth increasing velocity is restrained.